Art: Touch of Genius

When the doors of Christie's opened in London one day last week, a
full-house crowd was waiting to squeeze into the auction room. Up for
sale was a collection of 166 pictures, including Joseph Mallord William
Turner's seascape of Helvoetsluys, the Dutch port. For the fourth time
in a century, Londoners would get a chance to buy the painting that had
become a legendary symbol of the rivalry between England's two greatest
painters: Turner and John Constable.

Soon after Turner put what he thought were the finishing strokes to his
misty grey seascape in 1832, the painting was hung at the Royal...